Ralph is planning to use the same indoor rock climbing facility that his friend Trina did. Trina can't remember how long she climbed, but she spent a total of \$21. on her session. She paid a $ entrance fee and $3.25 for every hour she climbed. If Ralph wants to spend the same amount of money, write an equation to help him figure out how long he should plan on climbing. Highlight your equation in green. Then, solve the equation.